1. Field of the Invention
This invention relates to an artificial knee joint assembly, and more particularly to a safety artificial knee joint assembly, which can maintain a knee angle between a lower leg and a thigh when the assembly stands on a horizontal or inclined surface.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional artificial knee joint assembly 200 is shown to include a linkage unit 81 connected to a residual thigh 8, a support frame 82 disposed between the linkage unit-81 and a prosthetic lower leg 9, and a damping or hydraulic cylinder unit 83 disposed within the support frame 82. The hydraulic cylinder unit 83 includes a cylinder body 830, a piston 831 disposed movably within the cylinder body 830 so as to divide an interior space in the cylinder body 830 into upper and lower oil chambers 832, 833, and an oil passage 834 formed in the support frame 82 and in fluid communication with the upper and lower oil chambers 832, 833.
When the thigh 8 is raised to separate the artificial knee joint assembly 200 from the ground, as shown in FIG. 1, the lower leg 9 is inclined relative to the thigh 8. As such, the linkage unit 81 moves the piston 831 downwardly within the cylinder body 830, thereby permitting flow of some hydraulic oil from the lower oil chamber 833 into the upper oil chamber 832.
When the artificial knee joint assembly 200 stands on the ground, the linkage unit 81 will move the piston 831 upwardly from a lower limit position shown in FIG. 2 so as to cause some hydraulic oil to flow from the upper oil chamber 832 into the lower oil chamber 833. As such, the lower leg 9 is aligned with the thigh 8 so as to support the same. However, when standing on an inclined surface, the lower leg 9 is inclined relative to the thigh 8 so that the lower leg 9 cannot support the thigh 8, thereby resulting in tumbling of the prosthesis wearer.
The object of this invention is to provide a safety artificial knee joint assembly that can support effectively a residual thigh on a horizontal or inclined surface.
According to this invention, an artificial knee joint assembly includes a knee seat connected fixedly to a residual thigh, a support frame connected to the knee seat by means of a linkage unit, a prosthetic lower leg connected pivotally to a lower end of the support frame, a hydraulic cylinder unit disposed within the support frame so as to dampen the movement of the support frame relative to the knee seat, and a valve assembly disposed within the support frame. When the lower leg stands on a horizontal or inclined surface, the valve assembly is actuated by the lower leg to stop the operation of the hydraulic cylinder unit, thereby preventing rotation of the lower leg relative to the thigh.